FRP as a composite material made of resin reinforced by reinforcing fibers has been broadly utilized because it can exhibit strength and stiffness equal to or more than that of metal material while it is lighter than metal materials such as iron and aluminum.
Generally, FRP as a raw material comprises fiber bundle of single filaments and resin liquid and, therefore, the fiber bundle and the resin have to be composited in an FRP production process. Such a process might cause a problem that voids remain in final products because of incomplete composite of the fiber bundle and resin. Because voids remaining in products is an important element to control product quality of physical properties such as strength and stiffness and appearance, technologies are being developed to reduce voids from viewpoints of material and process.
Although a process in which resin adheres to and permeates into a fiber bundle is called an impregnation process, a resin-impregnated fiber bundle having desirable production time and porosity can hardly be produced simply by expecting that adhered resin sufficiently permeates into a fiber bundle by capillary action.
Pressure difference is one of the factors influencing resin impregnation ability in a fiber bundle. The impregnation ability can be improved by reducing the pressure of the atmosphere around the fiber bundle in addition to improving pressurization of the impregnating resin because impregnation efficiency is proportional to the pressure difference between the impregnating resin and air existing in the fiber bundle. Accordingly, it has been suggested that atmospheric pressure in a whole or a part of a production process of a resin-impregnated fiber bundle should be reduced to enhance impregnation efficiency.
A method disclosed in JP S60-240435 A to retain a whole production device in a decompression space to produce a resin-impregnated fiber bundle might increase the production cost because of the required strong decompression device to increase the decompression degree in a large decompression space.
A method disclosed in JP H5-96539 A and JP 2002-28924 A to decompress a part of the production process of a resin-impregnated fiber bundle might not keep spaces airtight because of fiber bundles transferring between the decompression space and ordinary pressure space. Although sealing should be achieved with a contact-type structure from a viewpoint of airtightness, fiber bundles passing by the contact-type sealing might fluff the fiber bundle by abrasion to degrade quality while plugging fluff might suspend the operation. Therefore, a noncontact-type sealing is often employed, but it has a poor airtightness so that a strong decompression device is also required to achieve a sufficient decompression degree.
Also, decompression spaces commonly disclosed in JP '435, JP '539 and JP '924 are not configured to consider workability. Namely, productivity might be degraded because devices have to be suspended and disassembled for maintenance for fluff plugging and fibers sticking inside the decompression section irregularly suspend operation.
Accordingly, it could be helpful to provide a process for producing a resin-impregnated fiber bundle, by which decompression is performed by a simple device, the airtightness is easily maintained and the decompression space is configured to have a good workability.